A typical inkjet printer typically uses a printhead assembly that includes one or more printheads. Each printhead has a plurality of inkjets from which drops of ink are ejected towards a recording medium. The inkjets of a printhead receive the ink from an ink manifold in the printhead that is supplied ink from a source, such as an ink reservoir or an ink cartridge. Each inkjet also includes an actuator positioned opposite an orifice, or nozzle, through which drops of ink are ejected. The nozzles of the inkjets may be formed in an aperture, or nozzle, plate that has openings corresponding to the nozzles of the inkjets. During operation, drop ejecting signals activate the actuators in the inkjets to expel drops of fluid through the inkjet nozzles onto the recording medium. By selectively activating the actuators of the inkjets to eject drops as the recording medium and printhead assembly move relative to each other, the deposited drops can be precisely patterned to form particular text and graphic images on the recording medium.
One difficulty faced by inkjet systems is the risk of sucking air or other contaminants, such as dust and paper fibers, into the printhead through the inkjet nozzles. These contaminants disrupt the fluidic path for the ink through the printhead. Such disruption from the air or contaminants can result in missing, undersized or misdirected drops on the recording media that degrade the print quality during printer operation, and even render one or more inkjets in the printhead completely inoperable. Air and other contaminants may enter the printhead nozzles in many situations. For example, negative pressures may develop within the printhead resulting in air being drawn in through the nozzles when the printhead is subjected to a sudden external impact or jolt, or when a hose is disconnected upstream of the printhead. In another example, negative pressure develops due to changing pressures in the external environment, such as when the printer is shipped in a shipping container. Consequently, printer improvements that help prevent air and other contaminants from entering a printhead are desirable.